Demagnetization of magnetic media by c doping for hdd patterned media application

ABSTRACT

Embodiments described herein provide methods and apparatus for treating a magnetic substrate having an imprinted, oxygen-reactive mask formed thereon by implanting ions into a magnetically active surface of the magnetic substrate through the imprinted oxygen-reactive mask, wherein the ions do not reduce the oxygen reactivity of the mask, and removing the mask by exposing the substrate to an oxygen-containing plasma. The mask may be amorphous carbon, through which carbon-containing ions are implanted into the magnetically active surface. The carbon-containing ions, which may also contain hydrogen, may be formed by activating a mixture of hydrocarbon gas and hydrogen. A ratio of the hydrogen and the hydrocarbon gas may be selected or adjusted to control the ion implantation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 61/576,655, filed Dec. 16, 2011, which is incorporated hereinby reference.

FIELD

Embodiments described herein relate to methods of manufacturing magneticmedia. More specifically, embodiments described herein relate topatterning of magnetic media by plasma exposure.

BACKGROUND

Magnetic media are used in various electronic devices such as hard diskdrives and magnetoresistive random access memory (MRAM) devices.Hard-disk drives are the storage medium of choice for computers andrelated devices. They are found in most desktop and laptop computers,and may also be found in a number of consumer electronic devices, suchas media recorders and players, and instruments for collecting andrecording data. Hard-disk drives are also deployed in arrays for networkstorage. MRAM devices are used in various non-volatile memory devices,such as flash drives and dynamic random access memory (DRAM) devices.

Magnetic media devices store and retrieve information using magneticfields. The disk in a hard-disk drive is configured with magneticdomains that are separately addressable by a magnetic head. The magnetichead moves into proximity with a magnetic domain and alters the magneticproperties of the domain to record information. To recover the recordedinformation, the magnetic head moves into proximity with the domain anddetects the magnetic properties of the domain. The magnetic propertiesof the domain are generally interpreted as corresponding to one of twopossible states, the “0” state and the “1” state. In this way, digitalinformation may be recorded on the magnetic medium and recoveredthereafter.

Magnetic storage media typically comprise a non-magnetic glass,composite glass/ceramic, or metal substrate with a magneticallysusceptible material between about 100 nm and about 1 μm thick depositedthereon by a deposition process, commonly a PVD or CVD process. In oneprocess, a layer comprising cobalt and platinum is sputter deposited ona structural substrate to form a magnetically active layer. Themagnetically susceptible layer is generally either deposited to form apattern, or is patterned after deposition, such that the surface of thedevice has areas of magnetic susceptibility interspersed with areas ofmagnetic inactivity denominated by orientation of their quantum spin.Where domains with different spin orientations meet, there is a regionreferred to as a Bloch wall in which the spin orientation goes through atransition from the first orientation to the second. The width of thistransition region limits the areal density of information storagebecause the Bloch wall occupies an increasing portion of the totalmagnetic domain.

To overcome the limit due to Bloch wall width in continuous magneticthin films, the domains can be physically separated by a non-magneticregion (which can be narrower than the width of a Bloch wall in acontinuous magnetic thin film). Conventional approaches for creatingdiscrete magnetic and non-magnetic areas on a medium have focused onforming single bit magnetic domains that are completely separate fromeach other, either by depositing the magnetic domains as separateislands or by removing material from a continuous magnetic film tophysically separate the magnetic domains. A patterned mask may beapplied to a non-magnetic substrate, and a magnetic material depositedover exposed portions of the non-magnetic substrate, or the magneticmaterial may be deposited before masking and patterning, and then etchedaway in exposed portions. By one method, the non-magnetic substrate istopographically patterned by etching or scribing, and the magneticallysusceptible material deposited by spin-coating or electroplating. Thedisk is then polished or planarized to expose the non-magneticboundaries around the magnetic domains. In some cases, the magneticmaterial is deposited in a patterned way to form magnetic grains or dotsseparated by a non-magnetic area.

Such methods are expected to yield storage structures capable ofsupporting data density up to about 1 TB/in², with individual domainshaving dimensions as small as 20 nm. All such methods typically resultin significant surface roughness of the medium. Altering the topographyof the substrate can become limiting because the read-write head of atypical hard-disk drive may fly as close as 2 nm from the surface of thedisk. Thus, there is a need for a process or method of patterningmagnetic media that has high resolution and does not alter thetopography of the media, and an apparatus for performing the process ormethod efficiently for high volume manufacturing.

SUMMARY

Embodiments described herein provide methods of treating a magneticsubstrate having an imprinted, oxygen-reactive mask formed thereon byimplanting ions into a magnetically active surface of the magneticsubstrate through the imprinted oxygen-reactive mask, wherein the ionsdo not reduce the oxygen reactivity of the mask. The mask is removed byexposing the substrate to an oxygen-containing plasma. The mask may beamorphous carbon, through which carbon-containing ions are implantedinto the magnetically active surface. The carbon-containing ions, whichmay also contain hydrogen, may be formed by activating a mixture ofhydrocarbon gas and hydrogen. A ratio of the hydrogen and thehydrocarbon gas may be selected or adjusted to control the ionimplantation.

Embodiments described herein also provide methods of treating asubstrate having a magnetically susceptible surface and an imprinted,oxygen-reactive barrier material formed on the magnetically susceptiblesurface, by disposing the substrate on a substrate support in aprocessing chamber, forming an activated gas mixture outside theprocessing chamber, flowing the activated gas mixture into theprocessing chamber, exposing the substrate to the activated gas mixture,implanting ions from the activated gas mixture into the magneticallysusceptible surface through openings, holes, or trench-like structuresin the barrier material by applying an electrical bias to the substrate,and exposing the substrate to an activated oxygen-containing gas toremove the barrier material, wherein the ions do not reduce the oxygenreactivity of the barrier material. The activated gas mixture may be acirculating plasma formed by applying RF power to a gas mixturecontaining carbon and hydrogen. A ratio of the hydrogen to the carbonmay be adjusted or selected to control the ion implantation.

Further embodiments described herein provide methods of forming apatterned magnetic substrate by forming a patterned resist on amagnetically active surface of a substrate, wherein the patterned resistdefines exposed portions and unexposed portions of the magneticallyactive surface, exposing the substrate to a carbon plasma, implantingcarbon ions from the carbon plasma into the exposed portions of themagnetically active surface, and removing the patterned resist byexposing the substrate to an oxygen plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a flow diagram summarizing a method according to oneembodiment.

FIG. 2 is a perspective view of a processing chamber operable topractice the methods described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Embodiments described herein generally provide methods and apparatus forforming a pattern of magnetic properties on a substrate. The substratesare generally metal, such as aluminum, or glass, and may be metal alloysor composite glass substances such as glass/ceramic blends. Thesubstrates are generally coated with a magnetically susceptible materialthat provides a medium for magnetic patterning. The magneticallysusceptible material may be formed in multiple layers, each layer havingthe same or different composition. In one embodiment, a first layer oflow coercivity magnetic material, such as iron or iron/nickel alloy, isformed over the base substrate, and a second layer of higher coercivitymagnetic material, such as a cobalt/nickel/platinum alloy, is formedover the first layer. These layers may be formed by any suitable methodknown to the art, such as physical vapor deposition, or sputtering,chemical vapor deposition, plasma-enhanced chemical vapor deposition,spin-coating, plating by electrochemical or electroless means, and thelike.

A resist material is formed over the magnetically susceptible surface,and a patterning process is used to form a physical pattern in theresist material. The patterning process is usually an imprint or contactstamping or printing process, but may be a lithographic or otherchemical process. The patterning process forms a mask from the resistmaterial, creating openings such as holes or trench-like structures inthe resist material that expose some areas of the magneticallysusceptible surface for a subsequent processing step while other areasremain covered by resist material. The exposed areas may be entirelyuncovered in some embodiments, while in other embodiments a thin layerof the resist material may be left covering the exposed areas.

A hardmask material may be used between the magnetically susceptiblesurface and the resist material, if desired. A hardmask may be moreresistant to pattern drift during the implant process in some cases. Thehardmask is patterned using the resist material as a mask, and then thehardmask is used to implant the magnetically susceptible surface.

Particles are implanted into the magnetically susceptible surface of thesubstrate, through the openings of the mask, to disrupt and/or changemagnetic properties of the magnetically susceptible surface in theexposed areas, while the protected areas are unchanged. The mask forms abarrier material substantially preventing particles from reaching theprotected areas of the substrate while allowing penetration of particlesin the exposed areas of the substrate. Changes to the structure of themagnetically susceptible surface alters atomic spin axes, changing thelocal magnetic properties in the affected area. In this way, a patternof magnetic properties is formed in the substrate surface that matchesthe pattern of the mask. The particles are typically formed as ions andaccelerated toward the substrate by applying an electric field, forexample by biasing the substrate. The particles may be partly orcompletely neutralized as they travel toward the substrate.

The topography of the magnetically susceptible surface is substantiallyunchanged by the patterning process because substantial quantities ofmaterial have not been added or removed from the magneticallysusceptible surface. Preserving the topography of the magneticallysusceptible surface is important in many applications because read/writestructures typically fly very close to moving magnetic storage surfaces,in some cases at an elevation of 5 nm or less. In such applications,variations in topography may result in increased collisions betweenstorage surfaces and read/write structures.

The mask is typically removed after the implant process. A chemicalremoval process is normally used. To avoid reducing susceptibility ofthe mask material, which may be a hardmask material, to chemical attack,the implanted particles are chosen to be chemically compatible with themask, or susceptible to attack using a similar chemistry, so that a highconcentration of the implanted particles in the mask material does notmake the mask difficult to remove.

As implant particles are directed toward the substrate, some of theimplant particles implant into, or deposit on, the mask. Suchimplantation and deposition may result in pattern drift as implantedions distort the atomic structure of the resist material and asdeposition alters the contours of the mask. To control such patterndrift during implantation, implant materials are chosen that arestructurally compatible with, or not structurally foreign to, the resistmaterial to minimize structural disruption of the resist material.Additionally, implant materials may be chosen that are easily removedwhen deposited on the mask.

FIG. 1 is a flow diagram summarizing a method according to oneembodiment. At 102, a patterned resist is formed on a magneticallyactive surface of a substrate. The substrate may be any substrate havinga magnetically active surface, such as any of the substrates describedabove. A magnetically active substrate is any substrate having ameasurable magnetic property, such as magnetism, magneticsusceptibility, or magnetic coercivity, that makes the substratemagnetizable to any substantial degree or indicates the presence of amagnetic field or magnetic force emanating from the surface. Amagnetically active surface may be a magnetically susceptible surface,or a surface having a magnetism or residual magnetism, or a surface withmagnetic coercivity that is not so high as to resist substantially allmagnetization. Materials used as storage media in magnetic storagedevices are all magnetically active and magnetically susceptiblematerials that may be treated according to the methods described herein.

The resist may be patterned by contact means or by chemical means. Theresist may be physically imprinted by direct contact with a solidtemplate, or by using chemical means such as lithography. Imprintresists are typically made of materials that may be physicallydepressed, shaped, stamped, or otherwise imprinted with a pattern, bysoftening at temperatures slightly above room temperature if necessary.Amorphous carbon, amorphous sulfur, and solder are examples of suchmaterials. Curable polymers that may be hardened after the pattern isimprinted may also be used. The patterned resist forms a mask thatexposes some areas of the substrate surface and covers other areas.

The resist material is typically a material that is not magneticallyactive, and is subject to chemical attack so that the resist can beremoved after patterning. Amorphous carbon and carbon-based polymers,for example, are examples of oxygen-reactive materials that may bestripped using an oxygen chemistry, for example by exposure to anoxygen-containing gas such as an oxygen plasma or an otherwise activeoxygen-containing mixture.

As noted above, the resist material may be formed on a hardmaskmaterial. A carbon hardmask material will be removable by a chemistrythat can remove the carbonaceous resist material. The carbon hardmaskmay be formed by a carbon deposition process, and may be patterned byusing the resist as a mask. The patterning process typically uses achemistry that may also attack the resist material, so the resistmaterial may be coated with a material that is not reactive to thechemistry used to etch the hardmask. In the case of a carbon hardmaskand carbon resist material, a silicon oxide layer may be blanketdeposited over the patterned resist material and then etched to exposethe tops of the resist pattern. The exposed resist may then be etchedthrough the carbon hardmask using an oxygen chemistry or other suitablechemistry to expose the magnetically susceptible layer.

At 104, the substrate is exposed to an implantation gas. Theimplantation gas is selected to be chemically or structurally compatiblewith the resist material such that incorporation of material from theimplantation gas in the resist material does not significantly distortthe microstructure of the resist material or alter its susceptibility tosubsequent removal. If a carbon-based resist material is used, theimplantation gas may be a carbon-containing gas, so that carbon atoms orcarbon-containing ions or particles from the gas that enter the resistmaterial will not create dislocations that substantially swell theresist material or otherwise distort the mask pattern. The implantationgas may be a mixture of hydrogen and a hydrocarbon, for example, becausecarbon and hydrogen are not structurally foreign to the carbon resistmaterial.

At 106, particles from the implantation gas are implanted into themagnetically active surface through the openings of the mask. Typically,the implantation gas is activated to produce ions that may beaccelerated toward the substrate by application of an electric field,for example by applying an electrical bias to the substrate. The ionsmay be fully or partially neutralized as they travel toward thesubstrate, so the particles implanted may be ions, neutral particlessuch as radicals, or a mixture thereof. The particles travel through themask, implanting into the magnetically active surface in the exposedareas, either directly or through a thin residual layer of resistmaterial left from the patterning process. The implanted particlesdisrupt the atomic structure of the magnetically active surface,changing one or more magnetic properties of the magnetically activesurface in the exposed areas according to the pattern of the resist.Measureable differences in the magnetic properties of domains in thesurface having dimensions from 1 nm to 50 nm may be achieved in thisway.

Particles from the implantation gas also interact with the resistmaterial, depositing on or implanting in the resist material on surfacesof the resist material parallel to the magnetically active surface,perpendicular to the magnetically active surface, and at all otherangles. To control any pattern drift due to interaction of theimplantation gas with the resist material, material may be removed fromthe mask surface by including a scavenging gas with the implantationgas. In the example above, hydrogen may be used as a scavenging gas forcarbon. Carbon-containing particles that deposit on the carbonaceousresist, on the thick areas of the mask, on the thin areas of the mask,or directly on the substrate surface in the mask openings may bescavenged by reaction with hydrogen in the implantation gas. The ratioof carbon to hydrogen, whether by volume, mass, or atomic equivalent,may be adjusted or selected to control the implantation by controllingany change to the pattern.

At 108, the resist material is removed using a dry stripping process.The resist material is exposed to a gas with which it reacts to form avolatile material that is removed from the chamber. According to themethods described herein, the implantation gas is selected so as not toreduce the chemical susceptibility of the resist material substantially.Continuing the example above, if amorphous carbon or carbon polymer isused as the resist material, and carbon ions and/or carbon-hydrogen ionsare used for implantation, the resist material retains susceptibility tooxygen attack, and may be readily removed by exposure to oxygen, whichmay be activated, for example by ionization into a plasma, to speed theremoval process. If a hardmask of compatible composition is used, thehardmask may also be removed in the same stripping process. For example,if a carbon hardmask is used with a carbon resist material, both may beremoved during a single stripping process.

The processes described above are typically conducted at lowtemperatures to avoid thermal modification of the magnetic properties ofthe substrate. The substrate temperature is typically maintained belowabout 150° C. Because implantation processes typically raise thetemperature of the substrate being processed, cooling is typicallyemployed. The substrate may be processed on a cooled substrate support,as is known in the art, or the substrate may be cooled periodically bydiscontinuing implantation and allowing the substrate to cool. Theimplantation gas may assist in cooling the substrate by collecting heatfrom the substrate as it flows across the substrate surface, or aseparate cooling gas may be employed. The rate of gas flow may beincreased to speed the cooling process, if desired.

In one embodiment, a substrate is coated with polyvinyl acetate (PVA)into which a pattern is physically imprinted by contact with a template.The substrate is an aluminum platter that has a layer of CoPtNi alloyabout 1 μm thick deposited thereon in a PVD process. The PVA isspin-coated onto the substrate, and the template contacted with the PVAlayer before the PVA hardens. The PVA firms while in contact with thetemplate, and fully hardens after the template is removed, yielding apatterned resist. The patterned resist has thick regions and thinregions, corresponding to protected areas of the substrate and exposedareas of the substrate. The thick regions are typically between about 50nm and about 100 nm thick, while the thin regions are typically betweenabout 1 nm and about 10 nm thick.

A carbon hardmask may be formed between the CoPtNi alloy layer and thePVA, if desired, by depositing an amorphous carbon layer using a PVD,CVD, or PECVD process. If a carbon hardmask is used, the carbon hardmaskmay be patterned after forming the patterned resist by depositing asilicon oxide layer over the patterned resist using a PVD, CVD, or PECVDprocess, etching the silicon oxide layer using a fluorine chemistry suchas HF to expose the resist, and then ashing the resist and the carbonhardmask to expose the CoPtNi alloy layer.

The substrate is positioned on a substrate support in a plasmaprocessing chamber. A P3i™ chamber available from Applied Materials,Inc., of Santa Clara, Calif., may be used for the plasma processingdescribed herein. An activated gas mixture is provided to a processingzone proximate to the substrate surface. The activated gas mixture is amixture of a hydrocarbon gas, such as methane or ethane, or acombination of hydrocarbons, and a hydrogen gas such as hydrogen orelemental hydrogen. An inert gas such as helium may also be included.The activated gas mixture is activated outside the processing chamber byexposing a gas mixture with one or more hydrocarbons, optionallyhydrogen, and optionally an inert gas to an electromagnetic field, suchas an electric field, a magnetic field, or a combined electric andmagnetic field (i.e. electromagnetic radiation). The electromagneticenergy may be applied in the form of RF power, DC power, or microwaveradiation, among other forms. Ions are generated, and the activated gasmixture flows into the processing chamber to interact with thesubstrate.

Methane gas is provided at a flow rate of 40 sccm in one embodimentwhere fourteen two-inch disks are processed simultaneously in a singlechamber. The methane gas is activated in a 400 W inductive RF source andflowed into the processing chamber. Hydrogen gas is included in a volumeratio of methane to hydrogen between about 0.1 and about 5.0, such asbetween about 1.0 and about 4.0, for example about 2.5. Helium gas isincluded in a volume ratio of methane to helium between about 0.1 andabout 5.0, such as between about 1.0 and about 4.0, for example about2.5. CF₄ may also be included in the gas mixture in a volume ratio ofmethane to CF₄ between about 1.0 and about 10.0, such as between about3.0 and about 8.0, for example about 5.5. B₂H₆ may also be included inthe gas mixture in a ratio of methane to B₂H₆ between about 2.0 andabout 3.0.

The ratio of methane and hydrogen in the activated gas may be adjustedor selected to control the implantation process by controlling patterndrift in the mask. As carbon from the activated gas mixture deposits onor implants into the mask, hydrogen from the activated gas mixturereacts with loosely bound carbon on the mask surface to form volatilespecies. Increasing the amount of hydrogen accelerates the process ofmaterial removal from the mask, if desired, controlling drift indimensions of the pattern.

An electric field is established proximate the substrate to acceleratethe ions toward the substrate surface. Hydrocarbon ions travel towardthe substrate surface and penetrate through the openings of the mask toimpact the magnetically active material in the exposed regions. Thehydrocarbon ions implant in, or deposit on, the mask above the protectedregions of the substrate surface. Continuing the example above, theelectric field is an RF bias between about 7 kV and about 10 kV, such asbetween about 7.5 kV and about 9.5 kV, for example about 8.5 kV, appliedto the substrate support. Pressure in the processing chamber ismaintained in a range of about 6-15 mTorr.

Implant progresses for 60-120 seconds, yielding a dose between about1×10¹⁷ ions/cm² and about 1×10¹⁸ ions/cm². A temperature of thesubstrate is monitored. If the temperature approaches 130° F. duringprocessing, exposure to the activated gas mixture, and biasing of thesubstrates, may be discontinued to allow the substrates to cool. Hightemperature is typically avoided during processing to avoid thermallydisrupting the magnetic properties of the substrate. Gas flow may becontinued through the processing chamber without activating the gasmixture to carry heat away from the substrates. In one embodiment, onlythe inert gas flow, for example helium, is continued during the coolingprocess. To speed the cooling process, gas flow through the chamber maybe increased. For example helium may be flowed through the chamber at aflow rate of 50 sLm for about 10 seconds to cool the substrates.Following the cooling period, the substrates may be exposed to theactivated gas mixture again to continue implantation, if desired. Theimplantation and cooling steps may be repeated any number of times in acycle until the desired implantation is complete.

The carbon mask may be removed by exposing the substrate to anoxygen-containing gas. The oxygen-containing gas may be activated andmay form a plasma, which may be an oxygen plasma. A gas mixturecontaining oxygen and optionally hydrogen and CF₄ may be activated byexposure to a magnetic field from the inductive RF source describedabove. The substrate is typically exposed to the oxygen-containing gasbetween about 30 seconds and about 5 minutes, depending on thereactivity of the oxygen-containing gas with the carbon mask.

During the implantation process 106 described above, material maycollect on internal chamber surfaces. Such material may be removedduring the resist removal process 108 described above. Each substrate orbatch of substrates may be overstripped to ensure the chamber surfacesare fully clean prior to processing the next substrate or batch, or thechamber may be cleaned after a number of implant processes areperformed. In a carbon implant embodiment, chamber cleaning may beimproved by seasoning the chamber surfaces with silicon oxide prior toimplantation processing by any convenient process. If desired, anoptical sensor may be deployed to determine an end point in the chamberclean process. The optical sensor may detect a difference in areflection or emission spectrum when carbon, or any other implantmaterials, covering the silicon oxide is removed.

Other materials may be used to mask and implant for magnetic patterning.For example, a physically patterned silicon oxide layer may be formed bysilane-peroxide deposition of liquid Si(OH)₄ near room temperature,contacting with a template, and warming to between 100° F. and 150° F.to polymerize. The template is removed before the silicon oxide layerfully hardens. Silicon may then be used to implant through the patternedsilicon oxide layer in a process similar to that described above, withhydrogen and/or fluorine controlling silicon deposition. An HFcontaining gas, which may be activated, may then be used to remove thesilicon oxide mask. Generally, use of a mask material that isstructurally and chemically compatible with the implant material affordsminimal pattern drift during implantation and control of any patterndrift that does occur, and predictable susceptibility to chemical attackso the mask may be readily removed after implantation.

FIG. 2 is an isometric view of a processing chamber 200 that may be usedto practice any of the methods described herein. The chamber of FIG. 2is useful for performing ion implantation procedures, but may also beused to shower a substrate with energetic ions without implanting. Theprocessing chamber 200 includes a chamber body 202 having a bottom 224,a top 226, and side walls 222 enclosing a process region 204. Asubstrate support assembly 228 is supported from the bottom 224 of thechamber body 202 and is adapted to receive a substrate 206 forprocessing. A gas distribution plate 230 is coupled to the top 226 ofthe chamber body 202 facing the substrate support assembly 228. Apumping port 232 is defined in the chamber body 202 and coupled to avacuum pump 234. The vacuum pump 234 is coupled through a throttle valve236 to the pumping port 232. A process gas source 252 is coupled to thegas distribution plate 230 to supply gaseous precursor compounds forprocesses performed on the substrate 206.

The chamber 200 depicted in FIG. 2 further includes a plasma source 290.The plasma source 290 includes a pair of separate external reentrantconduits 240, 240′ mounted on the outside of the top 226 of the chamberbody 202 disposed transverse to one another or orthogonal to oneanother. The first external conduit 240 has a first end 240 a coupledthrough an opening 298 formed in the top 226 into a first side of theprocess region 204 in the chamber body 202. A second end 240 b has anopening 296 coupled into a second side of the process region 204. Thesecond external reentrant conduit 240 b has a first end 240 a′ having anopening 294 coupled into a third side of the process region 204 and asecond end 240 b′ having an opening 292 into a fourth side of theprocess region 204. In one embodiment, the first and second externalreentrant conduits 240, 240′ are configured to be orthogonal to oneanother, thereby providing the two ends 240 a, 240 a′, 240 b, 240 b′ ofeach external reentrant conduits 240, 240′ disposed at about 90 degreeintervals around the periphery of the top 226 of the chamber body 202.The orthogonal configuration of the external reentrant conduits 240,240′ allows a plasma source distributed uniformly across the processregion 204. It is contemplated that the first and second externalreentrant conduits 240, 240′ may have other configurations utilized tocontrol plasma distribution in the process region 204.

Magnetically permeable torroidal cores 242, 242′ surround a portion of acorresponding one of the external reentrant conduits 240, 240′. Theconductive coils 244, 244′ are coupled to respective RF power sources246, 246′ through respective impedance match circuits or elements 248,248′. Each external reentrant conduits 240, 240′ is a hollow conductivetube interrupted by an insulating annular ring 250, 250′ respectivelythat interrupts an otherwise continuous electrical path between the twoends 240 a, 240 b (and 240 a′, 204 b′) of the respective externalreentrant conduits 240, 240′. Ion energy at the substrate surface iscontrolled by an RF bias generator 254 coupled to the substrate supportassembly 228 through an impedance match circuit or element 256.

Process gases including gaseous compounds supplied from the process gassource 252 are introduced through the overhead gas distribution plate230 into the process region 204. RF power source 246 is coupled from thepower applicators, i.e., core and coil, 242, 244 to gases supplied inthe conduit 240, which creates a circulating plasma current in a firstclosed torroidal path power source 246′ may be coupled from the otherpower applicators, i.e., core and coil, 242′, 244′ to gases in thesecond conduit 240′, which creates a circulating plasma current in asecond closed torroidal path transverse (e.g., orthogonal) to the firsttorroidal path. The second torroidal path includes the second externalreentrant conduit 240′ and the process region 204. The plasma currentsin each of the paths oscillate (e.g., reverse direction) at thefrequencies of the respective RF power sources 246, 246′, which may bethe same or slightly offset from one another.

Using the apparatus of FIG. 2, the methods described herein may beprocessed by forming an activated gas mixture outside the processingchamber and flowing the activated gas mixture into the processingchamber to apply to a substrate or substrates disposed therein. Theactivated gas may be formed into a circulating plasma that flows throughthe chamber in proximity to the substrate such that the electrical biasapplied to the substrate may capture ions from the circulating plasma.The circulating plasma may have a torroidal shape, and more than onecirculating plasma may be formed. For example, if two inductive sourcesare used, two circulating plasmas may form.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof.

1. A method of forming a patterned magnetic substrate, comprising:forming a patterned resist on a magnetically active surface of asubstrate, wherein the patterned resist defines exposed portions of themagnetically active surface; exposing the substrate to a carbon plasma;implanting carbon ions from the carbon plasma into the exposed portionsof the magnetically active surface; and removing the patterned resist byexposing the substrate to an oxygen plasma.
 2. The method of claim 1,wherein the carbon plasma comprises a mixture of hydrocarbons andhydrogen gas.
 3. The method of claim 1, wherein the patterned resistcomprises regions of high thickness and regions of low thickness, andthe regions of low thickness cover the exposed portions of themagnetically active surface.
 4. The method of claim 1, wherein thepatterned resist comprises amorphous carbon.
 5. The method of claim 1,further comprising maintaining a temperature of the substrate belowabout 150° C.
 6. The method of claim 5, wherein maintaining atemperature of the substrate below about 150° C. comprises discontinuingexposing the substrate to the carbon plasma when the temperature of thesubstrate is 130° C. or higher, cooling the substrate by flowing aninert gas across the substrate, and repeating exposing the substrate tothe carbon plasma and implanting carbon ions into the substrate.
 7. Themethod of claim 6, wherein the exposing, implanting, and cooling arerepeated sequentially until the substrate acquires the desired magneticpattern.
 8. A method of treating a magnetic substrate having animprinted, oxygen-reactive mask formed thereon, comprising: implantingions into a magnetically active surface of a magnetic substrate using animprinted oxygen-reactive mask to define a pattern on the magneticallyactive surface, wherein the ions do not reduce the oxygen reactivity ofthe mask; and removing the mask by exposing the substrate to anoxygen-containing plasma.
 9. The method of claim 8, wherein the maskcomprises amorphous carbon, and the ions are derived from a hydrocarbongas.
 10. The method of claim 8, wherein the implanting comprisesexposing the magnetically active surface to a circulating plasma formedfrom a gas mixture comprising a hydrocarbon gas.
 11. The method of claim9, wherein the implanting comprises forming a circulating plasma fromthe hydrocarbon gas.
 12. The method of claim 11, wherein the ionscomprise carbon and hydrogen.
 13. The method of claim 10, wherein thegas mixture further comprises B₂H₆.
 14. The method of claim 10, whereinthe gas mixture further comprises hydrogen gas.
 15. The method of claim14, wherein a ratio of the hydrogen gas to the hydrocarbon gas isselected or adjusted to control the ion implantation.
 16. A method oftreating a substrate having a magnetically susceptible surface and animprinted, oxygen-reactive barrier material formed on the magneticallysusceptible surface, the method comprising: disposing a substrate on asubstrate support in a processing chamber; forming an activated gasmixture outside the processing chamber, the activated gas mixturecomprising an oxygen-reactive material; flowing the activated gasmixture into the processing chamber; exposing the substrate to theactivated gas mixture; implanting ions from the activated gas mixtureinto the magnetically susceptible surface through the barrier materialby applying an electrical bias to the substrate; and exposing thesubstrate to an activated oxygen-containing gas to remove the barriermaterial, wherein the ions do not reduce the oxygen reactivity of thebarrier material.
 17. The method of claim 16, wherein each of thebarrier material and the activated gas mixture comprises carbon. 18.(canceled)
 19. The method of claim 16, wherein the activated gas mixtureis a torroidal plasma.
 20. The method of claim 17, wherein the activatedgas mixture is formed by applying RF power to a gas mixture comprising ahydrocarbon gas and a hydrogen gas.
 21. The method of claim 20, whereina ratio of the hydrogen gas to the hydrocarbon gas is adjusted orselected to control the ion implantation.